Building and maintaining a mobile communication network is not cheap and for this reason, users need to pay when they want to use a mobile communication network. Authentication in mobile networks is mandatory due to business and legal reasons, as well standards compliance. In order to verify that a user is authorized to use a mobile communication network, the user needs to transmit authentication information to the mobile communication network and this authentication information needs to comprise an identity. This identity may also be used for accounting purposes, e.g. if the user needs to pay per minute of calling and/or per MB of data usage.
In mobile communication networks such as GSM, UMTS and LTE, the identity that is transmitted in the authentication information is typically a user identity, e.g. an International Mobile Subscriber Identity (IMSI). In GSM, UMTS and LTE networks, the IMSI is provisioned in a Subscriber Identity Module (SIM) card. A drawback of the requirement to transmit this user identity is that it makes it easier to locate and track a user. Protocols used to authenticate the mobile network subscriber may address privacy issues to protect its identity from a passive eavesdropping over the radio network; however, the measures implemented this way have proven to be insufficient in a case when an adversary is capable of active signal interception (man in the middle attacks), and completely keep out of the scope threats from attackers that have access to the mobile network operator's equipment.
Most mobile phones use a single SIM card, but there are also certain models of mobile phones that are able to use two SIM cards. A mobile phone that is able to use two SIM cards is disclosed in EP 2 461 549 A1, for example. The benefit of using two SIM cards is that costs can be charged to a user's company for work calls and to the user himself for personal calls. However, even with two SIM cards, the user is relatively easy to locate and track, and the device's identification (IMEI number) remains persistent for each SIM card.